(a) Field of the Invention
The present invention relates to a cooling apparatus and method of an exhaust gas recirculation system.
(b) Description of the Related Art
Nitrogen oxides (NOx) are regulated pollutants. Exhaust gas recirculation (EGR) systems have recently been provided to address this. Generally, NOx is most prevalent when the air-fuel ratio is high. An exhaust gas recirculation system mixes some of the exhaust gas to the air-fuel mixture, reducing the amount of oxygen in the air-fuel mixture, and so lessening generation of NOx.
A hot-type EGR system retards ignition, lessens the air-fuel ratio, and lessens the amounts of particulate materials (PM) and hydrocarbons (HC), as well as the amount of NOx, while a cooled-type EGR system prevents combustion by cooling the exhaust gas and the combustion chamber. Recently, the hot EGR system and the cooled EGR system have been used together: the hot EGR system is used at low load and the cooled EGR system is used at high load.
Generally, temperature of exhaust gas is very high, and so a cooling apparatus is provided to the EGR system. The cooling apparatus should be made of a material that is durable at the high temperatures to which it is exposed. A typical material is stainless steel, which is very heavy and costly.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.